Carbamazepine - Krysiak Neuro exam 3

What is the therapeutic plasma concentration range for carbamazepine?

• 2-4 mg/L

• 10-20 mg/L

• 4-12 mg/L

• 8-14 mg/L

• 10-15 mg/L

Answer explanation

The therapeutic range for CBZ is typically 4-12 mg/mL. Any level greater then 8 mg/L is associated with CNS effects.

How long does it generally take for carbamazepine to complete autoinduction?

• 5-7 days

• 10-14 days

• 21-28 days

• 35-42 days

• 2 months

Answer explanation

CBZ induces its own metabolism, a process called autoinduction, which typically completes in 3-4 weeks (21-28 days).

How often should carbamazepine doses typically be adjusted during titration?

• Every 24 hours

• Every 48 hours

• Every 5-7 days

• Every 2-3 weeks

• Every 1-2 months

Answer explanation

Carbamazepine doses are increased every 2-3 weeks in 100-200 mg increments to allow for proper monitoring of therapeutic effects and to account for autoinduction

Which of the following factors warrants a dose reduction of carbamazepine?

• Child-Pugh score of 9

• Renal failure

• Concurrent use of phenytoin

• Elevated serum sodium

• Child-Pugh score of 5

Answer explanation

A Child-Pugh score ≥8 indicates moderate to severe hepatic impairment, requiring a 25-50% dose reduction due to reduced carbamazepine clearance​

Which of the following adverse effects are associated with carbamazepine therapy and should be monitored regularly? (SATA)

• Aplastic anemia

• Hyponatermia

• Hyperkalemia

• Steven-Johnson syndrome

• Renal failure

Answer explanation

CBZ carries a boxed warning for aplastic anemia, thrombocytopenia and agranulocytosis. It can cause hyponatremia due to antidiuretic effects and is linked to serious skin reactions like Stevens-Johnson syndrome.

Which of the following drugs can decrease carbamazepine levels by inducing CYP3A4? (three apply)

• St. Johns wort

• Rifampin

• Phenytoin

• Marcolide antibiotics

• Azole antifungals

Answer explanation

St. John’s Wort, rifampin, and phenytoin induce CYP3A4, leading to increased CBZ metabolism and decreased serum concentrations.

Azole antifungals and macrolides inhibit CYP3A4, increasing CBZ level

A 47-year-old male (85 kg) with tonic-clonic seizures is on carbamazepine 800 mg/day. His steady-state plasma concentration is 4.5 mcg/mL. The target therapeutic range is 6-8 mcg/mL. What dose adjustment is needed to bring the plasma concentration within the therapeutic range?

• Increase dose to 1600 mg/day

• Increase dose to 900 mg/day

• Increase dose to 1300 mg/day

• Decrease dose to 200 mg/day

• Discontinue carbamazepine

A 10-year-old boy (40 kg) with focal seizures is on CBZ 600 mg/day. His steady-state plasma concentration is 4.0 mcg/mL, and the target range is 6-8 mcg/mL. What is the appropriate dose adjustment?

• Increase dose to 800 mg/day

• Increase dose to 900 mg/day

• Increase dose to 1100 mg/day

• Decrease dose to 400 mg/day

• Maintain current dose

A 74-year-old female with complex seizures is stable on CBZ 1200 mg/day (400 mg TID). After starting diltiazem, she reports dizziness and confusion. Her CBZ level increased from 8 mcg/mL to 14 mcg/mL. The target range is 4-8 mcg/mL. What dose adjustment should be made to bring her back within the therapeutic range?

• Decrease dose to 800 mg/day

• Decrease dose to 700 mg/day

• Increase dose to 1400 mg/day

• Decrease the dose to 400 mg/day

• Decrease dose to 600 mg/day

A 60-year-old male with trigeminal neuralgia is on CBZ 1000 mg/day. He starts fluoxetine. After two weeks, he reports ataxia and blurred vision. His CBZ level is 12 mcg/mL. The target therapeutic range is 6-8 mcg/mL. What is the best dose adjustment?

• Decrease dose to 700 mg/day

• Decrease dose to 600 mg/day

• Decrease dose to 200 mg/day

• Increase dose to 1200 mg/day

• Decrease dose to 450 mg/day